Quoted-printable encoder and decoder

Use it free in the browser for mail debugging and MIME practice, or call the API at $0.002 per successful request when pipelines need reproducible quoted-printable transforms in CI and backend services.

What quoted-printable is and what this tool returns

Quoted-printable is a content-transfer encoding defined for MIME so mostly textual data can travel through 7-bit or restricted mail paths without becoming opaque Base64. Safe printable ASCII characters usually appear as themselves, the equals sign is reserved as the escape introducer, and any other octet is written as an equals sign followed by two hexadecimal digits. Soft line breaks — an equals sign at the end of a line before a CRLF — let encoders keep each encoded line within the classic seventy-six character limit without inserting hard newlines into the decoded text. This page always follows that contract for UTF-8 text: encode mode UTF-8 encodes your string, maps each byte to a literal or an equals-hex token, and inserts soft breaks so lines stay within the limit; decode mode removes soft breaks, expands equals-hex pairs into bytes, and rejects incomplete or non-hex escape sequences instead of guessing. The JSON response includes result for the transformed string, mode echoing encode or decode, encoding fixed to quoted-printable, and input_bytes plus output_bytes so you can assert sizes in tests. There is no streaming path and no silent repair of broken QP: either the string is valid quoted-printable text or the request fails with invalid_input. If you need opaque binary packing, prefer Base64 or Base64url endpoints; this landing is for the readable, email-oriented QP encoding that mail clients and MIME libraries already expect.

How text and mode are read and how results stay reproducible

Encode accepts any Unicode string, converts it with the platform TextEncoder to UTF-8 bytes, then emits quoted-printable with uppercase hex escapes and soft CRLF wraps. After bytes are recovered, a fatal UTF-8 decode ensures binary garbage does not become mojibake text. The preferred payload field is text, with aliases input, value, and s so forms, query strings, and SDK clients can reuse the same contract without renaming columns. Mode defaults to encode and accepts decode explicitly; aliases op, direction, and action map to the same switch for scripts that already use those names. Decode requires a well-formed QP string: a lone equals at the end of input, an equals followed by one character only, or an equals followed by non-hex digits all fail with a clear invalid_input message naming the malformed escape. Pair the free browser run on this page with the priced API when you need the identical mathematical result inside an automated pipeline without re-implementing quoted-printable tables yourself. Invalid inputs return invalid_input and are not charged, which keeps validation cheap while successful transforms remain a fixed item price.

Where quoted-printable fits in email, MIME, and test fixtures

Educators use the same tool when teaching the difference between Base64 opacity and quoted-printable readability for mostly textual payloads. On this page the work runs entirely in your browser; through the API each successful lookup costs $0.002, failed validation is not charged, and nothing is stored after the response returns. That split — free interactive exploration and a priced, identical API — matches the rest of the KIT tier-A catalog and lets you move from a classroom demo to an automated pipeline without changing the encoded result.